So if I get the 900/2100mHz version, can this be used on Virgin Mobile USA?

My fiance wants off of Android. She wants something smooth and reliable that won't have her frustrated all the time. She adores my Lumia Icon, but she's on Virgin Mobile (US) so things are tricky. Given that WP8.1 is here to relieve the pain of only having 4GB internal storage, I think this would work out just fine for her.

Since she's already got a Venue 8 Pro, she's looking to go knee-deep in the Windows ecosystem. I'm seeing that there's special versions of the HTC 8S that operate on the 900/2100 bands that Virgin Mobile likes... but it seems like those are only offered by Virgin Mobile Canada. She's not a gamer so I don't think the 512MB memory would bother her like it did me.

If I bought her an unlocked HTC 8S that has the 900/2100 bands, think Virgin Mobile would take it? I've had a Verizon iPhone flashed to work with PagePlus before, but I don't know if it'll be that simple here.